ML20195D442
| ML20195D442 | |
| Person / Time | |
|---|---|
| Site: | 07109206, 07109202 |
| Issue date: | 05/25/1999 |
| From: | TRANSNUCLEAR, INC. |
| To: | |
| Shared Package | |
| ML20195D432 | List: |
| References | |
| NUDOCS 9906090168 | |
| Download: ML20195D442 (27) | |
Text
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9
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BRP/ REG Full Fuel Load Transportation Feasibility Study L
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PDR C
t TABLE OF CONTENTS
' Section pege
- 1.0 - _ Introduction 1
2.0 Review License and Licensing Basis 2
2.1-Licensing History 2
2.2 NRC Comments of Basket Design (Full Loads) 2 2.3-NRC Licensing Basis (Half Loads).
3
. 3.0 Full Fuel Loads Licensing Approach and Recommendations 8
3.1 General Approach.
8 3.2
- Response to NRC Comments of Full Fuel Load Transportations 9
- 3.3 Recommendations 13 4.0 -
References 15 l
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y
.c y-LIST OF TABLE I
Page I
Table 1 Basket Stress Limits.
16 LIST OF FIGURES Figure 1 TN-BRP Basket Arrangement w/o Periphery inserts and Fuel Replacement Inserts 17 Figure 2 TN-REG Basket Arrangement w/o Periphery Inserts and Fuel Replacement Inserts 18 Figure 3 TN-BRP Basket Arrangement with Periphery inserts and Fuel Replacement Inserts 19 Figure 4 TN-REG Basket Arrangement with Periphery Inserts and Fuel Replacement inserts 20 Figure 5 TN-BRP Basket Arrangement with Periphery inserts 21 Figure 6 TN-REG Basket Arrangement with Periphery Insens 22 i
Figure 7 TN-BRP New Analysis -Drop Orientations 23 Figure 8 TN-REG New Analysis -Drop Orientations 24 I
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1.0 INTRODUCTION
This report provides technical support to the Nuclear Fuels Service Cask Demonstration Project. The TN-BRP and TN-REG casks are designed and licensed to transport and store spent nuclear fuel from the Big Rock Point and Robert E. Ginna nuclear power plants. Each cask is licensed to transport
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fuel (by NRC) in half of the available compartments (other compartments are filled with fuel replacement inserts). The casks are also licensed to store fuel (by DOE) in all of the available compartments. The TN-BRP has 44 BWR fuel compartments, each compartment can accommodate two BRP fuel assemblies stacked end-to-end. The TN-REG has 40 PWR fuel compartments. A total of 85 BWR fuel assemblies and 40 PWR fuel assemblies needed to be shipped. Therefore, two shipments to Idaho National Engineering and Environmental Laboratory are planned for each cask.
After the first shipment, the fuel will be removed and stored temporarily at INEEL. After the second shipment, the fuel in the cask will be left in place, the fuel replacement inserts will be removed and the temporarily stored fuel will be loaded in the casks, and the casks will be placed in storage.
Both the TN-BRP and TN-REG were designed to transport full fuel loads,85 fuel assemblies for l
TN-BRP (see Figure 1) and 40 fuel assemblies for TN-REG (see Figure 2), using a borated stainless
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steel fuel basket. The borated stainless steel, which provides structural strength and neutron poisoning, is the optimum material for the basket with respect to various features including cost, strength, and criticality. However, the NRC Transportation Certification Branch expressed concerns
- about the use of the borated stainless steel because it was not an ASME/ ASTM approved structural i
I material. Therefore, no credit was allowed for the borated stainless steel in the structural analysis of the basket. In order to maintain the validity of the criticality analysis, a halfload with fuel replacement inserts and basket peripheralinserts was required. The primary ftmetion of the fuel st pport structure is to maintain the fuel assembly payload geometry acceptable for criticality safety.
Ft.el assemblies will be loaded into in a checker-board type mrangement in the basket grid. The non-I fuel compartments in the grid will be filled with stainless steel replacement inserts to give the basket structuralintegrity. Peripheralinserts fabricated from an aluminum alby are positioned between the fuel basket and cask cavity wall (see Figures 3 and 4 for details). These alternate designs were approved by NRC on July 10,1989 for TN-BRP and May 15,1990 for TN-REG. They reduce the
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cask capacities to half and therefore two shipments are required for each cask.
j Subsequent to the NRC licensing the casks, borated stainless steel has become an ASTMm tandard s
material (A-887, approved in 1989) and ASME Section 111 Code Case 510A (approved in 1994) permits the construction of Component Support (NF)* and Core Support (NG)* structures with Grade A borated stainless steels (w/ boron contents not to exceed 1.74%). Code Case 510 also provides allowable e esses for these materials. The objective of this report is to determine ifit is
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n feasible to transport the casks with full fuel loads, BRP (85 assemblies) and REG (40 assemblies).
The following areas are addressed:
Review licenses and licensing basis Develop alternate approaches and identify the preferred approach.
Prepare report and recommendations.
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i 2.0 Review License and Licensing Basis 2.1 Licensing History Safety Analysis Reports for TN-BRPW and TN-REGW based on full load transportations, 85 fuel assemblies for TN.BRP and 40 fuel assemblies for TN-REG, were submitted to NRC for review. In i
these two Rev. O Safety Analysis Reports, the peripheral inserts and fuel replacement inserts were not included in the basket design.
The baskets are made of slotted borated stainless steel plates some of which are copper-coated for improved heat transfer. The baskets are constructed with these slotted plates interlocked to form an
" egg-crate" structure; to insure good mechanical properties the plates are not welded. Borated i
stainless steel was licensed and used in Europe for both spent fuel storage racks and for transport cask baskets. It had not been previously licensed for use in transport casks in the United States. The basket plate material, although not yet a " Code material", provides distinct advantages which permit the design to achieve maximum cask system performance objectives. Testing performed by Transnuclear demonstrated that material properties for the borated stainless steel were appropriate and justifiable for this application.
l 2.2 NRC Comments on the Basket Design (Full Loads)
Although several issues have been identified, the one concerning the basket may be the key issue with respect to pursuing the re-licensing of the basket for full fuel loads. The NRC requested Lawrence Livermore Laboratories to perfonn an independent structural analysis of the fuel basket.
m The results of that analysis and NRC's comments on the design of the basket using borated stainless steel are as follows:
a.
The basket is made of borated stainless steel. There are no established ASME-like standards for this material. Thus, the mechanical properties of this material are not uniform throughout the industry.
1 b.
Borated stainless steel does not have suflicient ductility to justify the use of stress
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allowables from the ASME or AISC codes. The analysis performed by Livermore indicates the stress in the basket exceeds the allowable values specified in those Codes.
c.
NRC is not aware of any accepted codes or standards which would permit the use of borated stainless steel as a structural member, particularly at high levels of stress and strain such as those that can be produced by the 30-foot drop test in 10CFR Part 71.
d.
The application did not include a fatigue evaluation of the material and the fatigue curves in the ASME code are not applicable.
The application did not consider brittle fracture. Because ofits relative low ductility and e.
the apparent decrease in ductility with increasing temperature, there is no established criteria for assuring adequate material toughness.
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j f.
The analysis in the application did not consider side drop orientations where the basket i
members are not parallel and perpendicular to the impact surface.
g.
The analysis performed by Livermore indicates that some portions of the basket are stressed beyond yield under the 30-foot drop test.
h.
The analysis performed by Livermore indicates that basket members are susceptible to buckling at various side drop orientations where the vasket members are not parallel and perpendicular to the impact surface.
i.
The application does not show that sufficient radial clearance exists between the ends of the basket.
2.3 NRC Licensing Basis (llalf Londs) 1 Based upon the lack of established standards for the borated stainless steel material, the absence of standards / criteria for its use in structural applications, the results of the Livermore analysis and the omission of fatigue and brittle failure evaluation, TN believed it was very unlikely that the use of borated stainless steel could be demonstratec for strength members in the fuel basket structure.
l Therefore, the Safety Analysis Reports of the TN-BRI" and TN-REGM were entirely rewritten. No l
structural credit is taken for the basket and no credit is taken for the basket material in accident criticality evaluation. In these revised Safety Analysis Reports, the criticality analysis of TN-BRP with a total payload of 44 fuel assemblies (20 fuel assemblies for TN-REG) demonstrate that criticality safety is assured with no credit taken for the structure of or presence of neutron poison in the fuel basket. Structural analyses demonstrate that the fuel replacement inserts and basket peripheral inserts remained intact to provide adequate fuel assembly spacing during worst normal transport and hypothetical accident loading conditions (see Figures 3 and 4 for details). The NRC licensing basis (halfload) of the TN-BRP and TN-REG are summarized as follows:
2.3.1 TN-B RP Packneine The TN-BRP cask is licensed for shipment of up to 44 BWR spent fuel assemblics. The total weight of the package is approximately 215,000 pounds. This includes the payload capacity of 41,250 pounds.
The spent fuel assemblies are positioned within a 44 compartment fuel basket. Each compartment can accommodate two BRP fuel assemblies stacked end-to-end. During transport, one-half the compartments are loaded with spent fuel and the remaining with stainless steel inserts. Peripheral inserts fabricated from an aluminum alloy are positioned between the fuel basket and cask cavity wall. The BWR fuel assemblies have a maximum burnup of 25,000 J
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. MWD /MTU. The minimum cooling time for any assembly is fourteen years. Maximum
. quantity ofmaterial per cask:
Forty-four BRP fuel assemblies Maximum decay heat per cask not to exceed 3.1 kilowatts. Maximum 103 watts per BRP fuel assembly.
l Structural s
The fuel basket is fabricated from borated stainless steel to provide a neutron absorber for
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criticality control. Because borated stainless steelis not an ASME Code approved structural material, no credit is taken for the borated stainless steel in the stmetural analysis of the basket.
The structural integrity of the basket during normal and accident conditions is based on an analysis of the stainless steel fuel replacement inserts and aluminum peripheral inserts. The structural analysis, however, shows that the fuel replacement inserts and basket peripheral inserts remain intact to provide adequate fuel assembly spacing for the normal and accident
- conditions.
Thermal i
The TN-BRP package is designed for a maximum internal heat load of 3.1 kilowatts. The decay heat source is developed using the ORIGEN fuel depletion Code for each of the eight types of fuel to be shipped. An axial peaking factor of 1.2 is used for each fuel assembly.
Minimum Temperatures The minimum temperatures in the cask are considered to be a uniform -40 F for the cold temperature analysis. No cask components would be adversely affected at this temperature except potentially the seals, which are not evaluated for an ambient temperature of-40"F.
The 0-ring used for r.ntainment is made from Viton V747-75 which maintains acceptable sealing characteristics at temperatures as low as -15 F. Shipments in the TN-BRP cask will be limited to dates between April 1 and October 31 to insure the seal temperatures stay within the
' allowable range.
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Maximum Pressure The maximum internal pressure for the cask is based on a peak cavity gas temperature of 385"F reached during the accident conditions. This produces a maximum pressure of 33 psia, assuming 100% release of the fission and rod fill gasses from the fuel rods. The design pressure for the cask is 60 psia.
Containment The TN-BRP cask will be used to transport eight difTerent types of spent fuel assemblies with burnups ranging up to 25,000 MWD /MTU. The most probable sources for radioactive reinse are fission gases leaking through fuel rod cladding, or crud adhering to fuel assemblies. The amount of fission gases produced for a 44 assembly shipment is estimated using the ORIGEN computer program. It is assumed that average fuel assembly has a burnup of 22,300 MWD /MTU and cooling time of 14 years.
I Shielding The radial shielding model of the cask consisted of a nominal thickness of 0.787" of aluminum and 9.62" of carbon steel The top and bottom shielding are 9.75" of carbon steel with a 26.25" thick impact limiter for the normal conditions.
The source term for a fuel assembly is broken into the three regions: the top end fittings, the fuel region and cladding, and the bottom end fittings. A full package payload consists of 44 fuel assemblies.
A burnup of 16,110 MWD /MTU is used at an assumed specific power of 25.9 MW/MTU. One
. irradiation cycle with no down time and a cooling period of 15 years is used (the latest fuel discharge date is 5/74).
Criticality The fuei basket is constructed of 0 276" thick,1.3% borated stainless steel plates that divide the cask cavity into 44 fuel compartments. Each compartment is 6.80" square and 170" long. The l
basket design includes a 1" gap between each quadrant which forms a flux trap when the cask l
cavity is flooded with water. The plates along the gap are covered on each side with 0.039" copper. Since borated stainless steel could not be shown to be an udequate structural material, the criticality analysis for the cask does not take credit for the boron neutron poison in the fuel basket
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I-Fuel assemblies will be loaded into alternating compartments, in a checker-board type arrangement. Two fuel assemblies, stacked end-to-end will be loaded into each fuel compartment.- Each of the non-fuel bearing compartments will be filled with a stainless steel replacement insert to provide positive spacing in the event of a basket failure.
2.3.2 TN-REG Packanine The TN-REG cask is licensed for shipment of up to 20 REG spent fuel assemblies. The total l
weight of the package is approximately 225,000 pounds. This includes the payload capacity of l
50,500 pounds.
l The spent fuel assemblies are positioned within a 40 compartment fuel basket. Each l
compartment can accommodate a single REG fuel assembly. During transport, one-half the compartments are loaded with spent fuel and the remaining with stainless ruelinserts.
Peripheral inserts fabricated from an aluminum alloy are positioned between the fuel basket and cask cavity wall.' The REG fuel assemblies have a maximum burnup of 15,000 MWD /MTU.
The minimum cooling time for any assembly is 17 years. Maximum quantity of material per cask:
j 1
Twenty PWR fuel assemblies Maximum decay heat per cask not to exceed 2.7 kilowatts. Maximum 135 watts per PWR fuel assembly.
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Structural j
The fuel basket is fabricated from borated stainless steel to provide a neutron absorber for criticality control. Because borated stainless steelis not an ASME Code approved structural material, no credit is taken for the borated stainless steel in the structural analysis of the basket.
The stmetural integrity of the basket during normal and accident conditions is based on an analysis of the stainless steel fuel replacement inserts and aluminum peripheral inserts. The stmetural analysis, however, shows that the fuel replacement inserts and basket peripheral l
inserts remain intact to provide adequate fuel assembly spacing for the normal and accident conditions.
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e Thermal The TN-REG package is designed for a maximum internal heat load of 2.7 kilowatts. The decay heat source was developed using the ORIGEN fuel depletion Code for each of the eight types of fuel to be shippedc An axial peaking factor of 1.2 is used for each fuel assembly.
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Minimum Temperatures l
The minimum temperatures in the cask are considered to be a uniform -40"F for the cold temperature analysis. No cask components would be adversely atrected at this temperature except po:entially the seals, which are not evaluated for an ambient temperature of-40 F.
l The 0-ring used for containment is made from Viton V747-75 which maintains acceptable sealing characteristics at temperatures as low as -15 F. Shipments in the TN-REG cask will be limited to dates between April 1 and October 31 to insure the seal temperatures stay within the allowable range.
Maximum Pressure The maximum internal pressure for the cask is based on a peak cavity gas temperature of 349"F reached during the accident conditions. This produces a maximum pressure of 26 psia, assuming 100% release of the fission and rod fill gasses from the fuel rods. The design pressure for the cask is 60 psia.
Containment The TN-REG cask will be used to transport one type of spent fuel assemblies with burnups ranging up to 15,000 MWD /MTU. The most probable sources for radioactive release are fission gases leaking through fuel rod cladding, or crud adhering to fuel assemblies. The amount of fission gases produced for a 20 assembly shipment is estimated using the ORIGEN computer program. It is assumed that average fuel assembly has an burnup of 11,537 MWD /MTU and cooling time of17 years.
Shieldine
.The cask wall has a nominal thickness of 9.25" Additional radial shielding is provided by the fuel basket (50% of the mass) and the basket peripheral inserts (a thickness of 0.787" around the inside of the cask). The cask bottom has a nominal thickness of 8.25" and the lid has a nominal thickness of 8.5" Each end of the cask is covered by an impact limiter which has a 26" NMvpkloc\\2283jae.wpl l l
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e thickness of redwood. The red wood is encased in a 0.23" thick steel shell. It is assumed that the irradiation occurred in one cycle with no down time during the cycle. All of the fuel is assumed to have an initial enrichment of 3.48% and a total uranium loading of 382 kgs per assembly The specific power is 37.5 MW/MTU with a total burnup of 11,537 MWD /MTU.
The cooling time is 17 years.
- Neutron source contributions from spontaneous fission and alpha-n reactions are included.
Subcritical neutron multiplication is accounted for by adjusting for the k-efTof the dry cask.
The source term for a fuel assembly is broken into the three regions: the top end fittings, the fuel region and cladding, and the bottom end fittings. A full package payload consists of 20 fuel assemblies.
Criticality The fuel basket is constnicted of 0.276" thick,1.7% borated stainless steel plates that divide the cask cavity into 40 fuel compartments. Each compartment is 8.05" square and 163.25" long.
The basket design includes two 1" gaps and a 2" gap which form flux traps when the cask cavity is flooded with water. The plates along the gap are covered on each side with 0.02" copper.
Since borated stainless steel could not be shown to be an adequate structural material, the criticality analysis for the cask does not take credit for the baron neutron poison in the fuel basket.
Fuel assemblies will be loaded into in a checker-board type arrangement in the basket grid. The non-fuel compartments in the grid will be filled with a stainless steel replacement insert to give the basket stnictural integrity.
3.0 Full Fuel Load Licensing Approach and Recommendations 3.1 General Approach i
l Transnuclear's general approach to NRC cutification entails early defmition of the key technical issues, proactive and ongoing interaction with the NRC on these issues, development of a technical i
l approach that appropriately resolves the key issues, and preparation of a Certification Plan to formalize the approach and timing and to permit progress monitoring.
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The two key issues needed to be resolved for licensing the TN-BRP and TN-REG for full fuel loads transportations are:
1 l
a.
Qualification of borated stainless steel as a basket material acceptable to NRC for transport conditions (NRC comments 2.2, a-c). TN believes that this key issue is still a major hurdle, I
because the borated stainless steels used in TN BRP and TN-REG baskets are manufactured from two different processes; borated stainless steel for TN-BIU) basket is a wrought plate product (ASTM designated as Grade B material), and borated stainless steel for TN-REG basket is a powder metallurgy product (ASTM designated as Grade A material). Although both of these two types of materials are included in the ASTM Standard Specification (A887-89), only borated stainless steels manufactured from powder j
metallurgy product and boron contents up to 1.74% are approved in Code Case #510. TN-l BRP basket is fabricated from Grade B borated stainless steel and TN-REG is fabricated l
from Grade A borated stainless steel with boron content exceeding 1.74% (1.8% nominal).
Neither of these borated stainless steels are approved in the Code Case #510.
1 b.
Based upon current analysis methods and the proposed design, identify the additional analysis requiremem to satisfy the structural requirements (NRC comments 2.2, d-i).
1 l
l In order to ensure effective communication and progress, these issues will be the subject of a meeting
- with NRC. This meeting will provide NRC stafTreviewers the oppodunity to comment on the i
proposed approach. The Certification Plan will then document, for this as well as other issues, the t
I major objectives, methods, milestones, and schedule associated with achieving resolution and subsequent certification.
l 3.2 Response to NRC Comments of Full Fuel Loads Transportations The following describes Transnuclear's proposed approach to respond to the NRC comments on the original full fuel loads Safety Analysis Reports. These comments are applied to both TN-BRP and i
TN-REG.
l l
NRC Comments: The basket is made of horated stainless steel. There are no established l
ASME-like standards for this material. Thus, the mechanical properties of this material are not uniform throughout the industry.
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' Response:
l Borated' stainless steel has become an ASTM standard material (A-887, approved in 1989).
e' l ASME Section 111 Code Case 510 (approved in 1994) permits the construction of Component Support (NF) and Core Suppon (NG) structures with Grade A borated stainless steels.
. The material properties of TN-BRP and TN-REG are established by tests on the actual plate material used for the basket. The material properties (yield and tensile strength) from the test are better than specified by the ASTM and Code Case 510 and are listed in the -
' following table for comparison.
Comnarison of Borated Stainless Steel Properties Temperature l Test Value "* -
Test Value '">
ASTM A-887")
(TN BRP)
(TN-REG)
Type 304B6 Nuclear Code Cr Ni Stainless Cr Ni Stainless Cr-Ni Stainless Case 510 * ~
)
W/1.43% Boron W/1.8% Boron W/l.5-1.74 Boron Type 30486 l
I S
Room Temp.
50 56 30 30 y
non 650"F.
44 47 23.7 S,, -
Room Temp.
95 -
112 75 75 w
650"F 81 100 68.6 Elongation Room Temp.
15.6 19.8 20 in 2" (%)
650'F 14 18 I
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i NRC Comment:
Borated stainless steel does not have sufficient ductility to justify the use of stress allowables from the ASME or AISC codes. The analysis performed by Livermore indicates the stress in basket exceed the allowable values specified in those code.
l
Response
The borated stainless steel used in the TN-BRP and TN-REG baskets has suflicient i
ductility for its intended use.
Depending on boron concentration, manufacturing process and strain rate, the elongation at rupture may be low in comparison to " pure" stainless steel. However, austenitic steel has unusually high elongation (30-40%) in comparison with that oflow alloy steels and ferritic stainless steel (20%) or high strength steel (10%), which are in every day use in pressure vessels and support stmetures.
The borated stainless steel used in TN-BRP and TN-REG consist of a dispersion of L
chromium boride particles in an austenitic stainless steel matrix. The efTect of these particles is to increase tensile strength with a reduction in elongation. The increase in tensile strength is a desirable feature while elongation must be held to acceptable minimum values. With the borated stainless steel used in the BRP and REG baskets, existing test data show that elongations are on the order of 14-20%. This value is in good comparison with the value specified by ASTM A-887.
The analysis performed by LLNL was based on a finite element model without peripheral inserts. It is proposed to include the aluminum peripheralinserts in the new analysis. The extra inserts reduce the unbraced length of *he basket panels and reduce the tendency of the panel to experience out-of-plane deformation, which will reduce the panel stresses.
i NRC Comment: NRC is not aware of any accepted codes or standards which would permit the use of borated stainless steel as a structural member, particularly at high levels of stress and strain such as those that can be produced by the 30-foot drop test in 10CFR Part 71.
Response
Based on recent Nuclear Code Case (Code Case #510) ASTM A887-89, Grade A (Types 304B,304B1 to 6) borated stainless steels which are not welded are acceptable for basket structural materials.
NRC Comment: The application did not include a fatigue evaluation of the material and the fatigue curves in the ASME code are not applicable.
Response
It is proposed that fatigue evaluation should be included in the new analysis.
l l
l N:\\wph\\2283jae.wpd d
Code Case 510 not only provides allowable stress for Grade A borated stainless steel but also provides a fatigue curve for fatigue evaluation.
NRC Comment: The application did not consider brittle fracture. Because ofits relative low ductility and the apparent decrease in ductility with increasing temperature, there is no established criteria for assuring adequate material toughness.
Response
The brittle fracture had not been explicitly addressed because:
j The borated stainless steel is sufficiently ductile. The existing test data shows that e
elongations on the order of 14-20% even at high temperatures.
j The TN-BRP and TN-REG basket plates have been designed and fabricated to exclude sharp notches, discontinuities and welds.
1 NRC Comment: The analysis in the application did not consider side drop orientations where the basket members are not parallel and perpendicular to the impact surface, j
i
Response
lt is proposed that a new analysis will evaluate side drop orientations (three difTerent orientations) where the basket members are not parallel and perpendicular to the impact surface.
NRC Comments: The analysis performed by Livermore indicates that some portions of the basket are stressed beyond yield under the 30-foot drop test.
Response
It should be noted that local yielding is permitted in some portion of the basket under the 30-foot accident drop conditions as long as no plate fracture occurs and each fuel assembly remains surrounded by the plates.
The new analyses will evaluate stresses against ASME B&PV Code allowables (Subsection NG and Appendix F).
l t
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NRC Comment: The analysis performed by Livermore indicates that basket members are susceptible to buckling at various side drop orientations where the basket members are not parallel and perpendicular to the impact surface.
Response
It is proposed that a new analysis (including the aluminum peripheral inserts) will be included to evaluate side drop orientations where the basket members are not parallel and perpendicular to the impact surface.
NRC Comments: The application does not show that sufficient radial clearance exists between the ends of the basket.
Response
It is proposed that a new calculation will be performed to demonstrate that sufficient radial clearances exist between the ends of the basket mernbers and the inner surface of the cask to prevent the occurrence of thermal stresses. Accuracy of thermal analysis and actual dimensions of the basket plates and cask cavity will be considered in the free expansion analysis. The thermal analysis may need to be revised to take credit for current decay heat of the fuel, which has decreased since the last analysis.
3.3 Recommendations A meeting with NRC will be arranged to resolve the qualification of borated stainless steel as a basket matenal for transport conditions. Following is the detailed technical approach to resolve additional NRC concerns:
Design Methodology and Desien Criteria of the Hasket it is proposed to utilize the design rules of the ASME Code, Section Ill, Division 1, Subsection NG-Core Support Structures for the design of the borated stainless steel fuel basket. The Subsection NG rules have been developed specifically for structures which are designed to provide direct support or restraint of fuel assemblies within a reactor pressure vessel. The most severe loads for core support structures, like those for fuel baskets in transport casks, usually result from abnormal rather than normal load conditions. The prevention of criticality is the design function of both.
l A NRC sponsored study performed by Lawrence Livermore National Laboratory (NUREG/CR-3854) provides further support for this approach. This report concludes that acceptable criteria for the NAupklx\\2283jaeupd,
~
V fabrication of criticality components (fuel basket) for spent fuel shipping containers are contained in the
- ASME Code, Section Ill, Division I, Subsection NG.
Subsection NG provides design-by-analysis rules for calculating stresses and defmes allowable stress limits. When evaluating the results from nonlinear elastic-plastic analysis for the Level D (accident) conditions, the stress limits are in accordance with Appendix F of Section 111 of the Code. The stress limits for the basket are summarized in Table 1.
New Analysis Reauired The structural adequacy of the basket design will be demonstrated by analysis. It is proposed to include the aluminum peripheral inserts in the new analysis (see Figures 5 and 6). The inserts in the basket periphery will reduce the basket deformation and stress.
The acceleration loads will be modeled as constant inertial g-loads. The static load will be applied to the basket as a uniformly distributed ioad,_whose magnitude will be a simple product of the mass times the maximum acceleration (LLNL employed the same assumptions in their analyses).
Analyses will be performed for three (3) different loading orientations relative to the basket j
plates: 0,30, and 45 Figures 7 and 8 show these loadmg onentations.
)
l Use material properties from ASTM Specification combined with data obtained from testing for structural analysis (these values are lower than those used in the original full load applications).
Fatigue curve from Code Case 510 will be used for fatigue evaluation of the basket, i
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4.0 References.
l-1.
1989 ASTM " Standard Specification for Borated Stainless Steel Plates, Sheet, and Stiip for Nuclear Application, A887-89 (Reapproved 1994)."
2.
1995 ASME B&PV Code, Nuclear Components, Code Case N-510-1 " Borated Stainless Steel for Class CS Core Support Structures and Class 1 Component Supports, Section 111, Division 1."
3.
ASME B&PV, Section 111, Subsection NF-Supports.
4.
ASME B&PV, Section 111, Subsection NG - Core Support Structures.
5.
TN-BRP Spent Fuel Package, Safety Analysis Repoit for Transport, dated September 13,1985.
6.
TN-REG Spent Fuel Package, Safety Analysis Report for Transport, dated October 25,1985.
7.
Letter from Charles MacDonald of NRC to Carl Gertz of DOE "FCTC:CEM 71-9202, dated February.12,1986".
8.
TN-BRP Spent Fuel Package, Safety Analysis Report for Transport, dated January,1989.
9.
TN-REG Spent Fuel Package, Safety Analysis Report for Transport, dated September,1989.
- 10. Final Documentation for Boron Alloyed Steel Plates. Project No. 3010, TN-BRP Transport / Storage Cask, by Vereinigte Edelstahlwerke Aktiengesellschaft (VEW).
I1. Certificate of Tests for CR-N1 Stainless w/ Boron 1.8% Het Rolled Annealed, Descaled, by Carpenter Technology Corporation.-
- 12. Transnuclear Spent Fuel Storage / Transport Cask Basket structural analysis, by Sandia National Laboratories, dated July 8,1987.
i r
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i 1
4 Table i Basket Stress' Limits Stress Category Allowable Stresses Normal Accident Condition #
Conditions * -
Primary Membrane Lesser of General P,1 S.
2.4 S. or 0.7 S,m
. Local P.
1.5 S,,,
3.6 S,,, or S,, M i
15 mary Membrane + Bending Lesser of (P. or P ) + P.
1.5 S.
3.6 S,,, or S M i
Range of Primary + Secondary 3.0 S,,, -
2S, for 10 cyclesW
_ _ _ P,,, or P.) + P. + 0
(
i Hearing Stress S
Not applicable y
Pure Shear Stress 0.6 S,,
0.42 S,,
Buckling Compressive 2/3 clastic buckling loud or Stress limit per 100% of plastic analysis collapse load or NF 3322.l(c)
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